<template>
  <div>
    <router-link 
    tag="div" to="/" 
    class="header-abs"
    v-show="showAbs">
      <span class="iconfont header-abs-back">&#xe624;</span>
    </router-link>
    <div class="header-fixed" 
    v-show="!showAbs"
    :style="opacityStyle">
      <router-link to="/">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
      景点详情
    </div>
  </div>
</template>
<script>
export default {
  name: "DetailHeader",
  data (){
      return {
          showAbs:true,
          opacityStyle:{
              opacity:0
          }
      }
  },
  methods:{
     handleScroll () {
        const top = document.documentElement.scrollTop
        if(top > 60 ){
            let opacity = top /140
            opacity = opacity > 1?1:opacity
            this.opacityStyle = {
                opacity
            }
            this.showAbs = false
        }else{
            this.showAbs = true
        }
     }
  },
  activated (){
      window.addEventListener('scroll',this.handleScroll)
  },
//   对上面的window绑定的事件进行解绑
  deactivated (){
      window.removeEventListener('scroll',this.handleScroll)
  }

};
</script>
<style scoped>
.header-abs{
    position: absolute;
    left: .2rem;
    top: .2rem;
    width: .8rem;
    height: .8rem;
    border-radius: .4rem;
    background: rgba(0, 0, 0, .8);
    line-height: .8rem;
    text-align: center;
}
.header-abs-back{
    color: #fff;
    font-size: .4rem;
}
.header-fixed{
 z-index: 2;
  position: fixed;
  height: 0.86rem;
  line-height: 0.86rem;
  text-align: center;
  color: #fff;
  background: #00bcd4;
  font-size: 20px;
  top: 0;
  left: 0;
  right: 0;
}
.header-fixed-back{
      position: absolute;
      top: 0;
      left: 0;
      width: .64rem;
      text-align: center;
      font-size: .4rem;
      color: #fff;
}
</style>
